Question 1

When can I turn on underfloor heating after screeding?

Accepted Answer

For anhydrite screed, allow a minimum of 7 days (preferably 21 days) before starting commissioning. For sand:cement screed, the minimum is 21 days. The laitance must be removed from anhydrite before commissioning.

Question 2

What temperature ramp rate should I use?

Accepted Answer

Increase the flow temperature by no more than 5°C per day, starting at 25°C. This gradual increase prevents thermal shock and cracking. Once at maximum temperature, hold for at least 3 days.

Question 3

What moisture level should screed reach before laying flooring?

Accepted Answer

For tiles on anhydrite: ≤0.5% CM (carbide method). For wood/laminate: ≤1.0% CM or ≤75% RH. Test at multiple locations across the floor, especially in corners and near external walls.

Question 4

How long does screed commissioning take?

Accepted Answer

Total commissioning time is typically 40–60 days: 21–40 days initial drying + 4–8 days ramp up + 3 days hold + 4–8 days ramp down. Fast-drying screeds can reduce the initial drying period.

Question 5

Do I need to commission screed if using electric UFH?

Accepted Answer

Yes. Any screed over underfloor heating (wet or electric) needs the same commissioning procedure. The screed must be dried out gradually to prevent cracking and ensure proper moisture levels.

Heated Screed Commissioning Calculator — Drying & Ramp Schedule

How We Calculate This

The schedule

Frequently Asked Questions

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